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Agriculture & Natural Resources

Discourage Plant Diseases in the Home Garden

Spraying with chemical fungicides is often important and/or necessary to control certain diseases in the home vegetable garden, flower garden, on shrubs, ornamental and fruit trees. However, fungicides are only one of the many tools that can be used to combat plant diseases. Application of the following suggestions will help to reduce the incidence and severity of diseases in your garden:

Select a suitable location for planting. Some plants like sunny locations while others prefer more shade. Avoid extremely wet soils since they favor many root diseases. Improving drainage, where possible, will reduce these diseases. Plant the right plant in the right place.

Practice rotation within your vegetable garden plot. If possible, change your garden location occasionally. This helps prevent the build-up of disease-causing organisms. Select disease resistant varieties or cultivars where they are available. Check with your nurseryman or garden-center operator about this important matter before making a purchase.

Use only disease-free seed and transplants. Buy from a reputable seed company, greenhouse-operator or nurseryman. Do not accept any plants (even at bargain prices) that appear unhealthy. Remember that many disease-causing organisms can be carried to your garden on seeds and transplants.

Improve the soil by incorporating organic matter such as compost, manure, etc. Increased organic matter improves soil structure, moisture-holding capacity and nutrient content as well as encouraging healthy, balanced populations of soil organisms. A healthy soil will discourage plant pathogens that can infect garden plants.

Fertilize your garden on the basis of soil test results. Plants that are too weak or too vigorous, as a result of improper fertilization, will be more subject to diseases.

Do not over-crowd plants. This results in high humidity beneath the plant canopy which favors certain diseases such as downy mildew, Botrytis blight, etc. Thin plants to permit free air circulation. Water properly. Try to maintain an even water supply and avoid dry-wet fluctuations. Avoid watering late in the day since this will favor disease conditions. Remember that too much moisture will favor several root and foliage diseases. When watering with a hose, try to wet the soil, not the plants.

Control weeds in and near the garden. Weeds help create a micro-climate that is ideal for development of fungus and bacterial diseases. They may also provide the initial source for certain virus diseases.

Control insect pests. They may carry and spread certain virus and bacterial diseases.

Destroy badly diseased plants or plant parts as soon as you observe them in your garden. Otherwise, they may serve as a source of spread to other plants. Except for plants that die from a wilt disease, all other diseased plants can be composted.

Spade under or remove and compost crop refuse as soon as possible after you harvest your garden. This promotes elimination of disease-causing organisms which could overwinter in crop debris left in the garden.

Remove and destroy diseased tree and shrub branches before a disease spreads. It is a wise policy to always prune-out-diseased plant tissues during the dormant period of fall or spring. Fallen tree leaves should be raked up and composted or cut into small pieces with a lawn mower and left on the lawn to decompose. Intact leaves left in the yard could be a source of disease-causing fungi or bacteria if left from one season to another.

These practices, carefully followed, will help you avoid destructive plant diseases in the home garden. Contact your county Extension agent for more information concerning specific plant diseases and their control.

Caution: The information and recommendations in these fact sheets were developed for Delaware conditions and may not apply in other areas.

Revision Date: 4/1/2004
Bob Mulrooney, Extension Plant Pathologist
PP-24